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Production
Published in Wanda Grimsgaard, Design and Strategy, 2023
Paper is made in large paper mills. For instance, the paper machine in Munkedal, Sweden, is 80 metres long.16 Papermaking usually starts by feeding the pulp into a long paper machine, where the pulp is sprayed onto a wire where the water is sucked out. In this process, the wood fibres orient themselves in the direction of the paper web. This way, the fibre direction is formed in the paper. Afterwards, the water is pressed out using a straining cloth. The pressure to which the paper is subjected affects the bulk, stiffness, opacity, strength, and roughness of the finished paper. After that, the fresh paper passes over heat rollers, which further dry the paper. Finally, the paper is surface treated with a thin film of adhesive, usually starch, to give the surface extra strength and improve printability. At this stage, the paper is called uncoated paper.17 Through further processing a thin layer of latex, clay, and some other substances can be applied to the paper to make the surface even more print friendly.18 We are then talking about coated paper. Finally, the paper is wound onto large tambour reels, and then cut down into smaller reels or sheets, which are delivered for printing or other purposes. The entire process in the paper machine takes only 10 to 30 seconds.
Beneficial Industrial Uses of Electricity: Industrial Introduction and Process Industries
Published in Clark W. Gellings, 2 Emissions with Electricity, 2020
All other paper machine components are designed to remove water or surface treat the paper or paper-board after the stock layer is formed. Although there are many variations, the following three stages of water removal are typically used. In the first stage after the headbox, the dilute suspension of mainly fibers and sometimes mineral fillers is subjected to water drainage through one or more porous continuously rotating belts called wires. In the second phase of the water removal, pressing, the fibrous web is pressed in up to four nips to remove water mechanically. Sometimes the web is heated with direct steam to aid water removal during this stage. The third stage of water removal is drying in which the remaining water is removed through an evaporative drying process. The amount of water removed decreases in each successive stage, and the costs of removing the water increase considerably with each stage. At the dry end of the paper machine, the moisture content is typically around 4 to 8%—close to the natural moisture content of paper or board stock in ambient air. The dry paper is wound continuously onto a reel spool the same width as the paper machine.
Effect of dryer fabric structure on the performance of contact paper drying
Published in Drying Technology, 2019
Amir Farzad Forughi, Sheldon Green, Boris Stoeber
Most paper machines have three major operational stages—the forming section, in which a wet paper mat is made from a pulp slurry; the press section, in which the pulp mat is mechanically dewatered and consolidated; and the drying section, in which the paper moisture content (MC) is reduced through evaporation from about 130% to about 8% by weight. Here, the MC is defined as the mass of water per mass of dry paper. The 50–80% of total energy in paper production from pulp is consumed by the drying section.[1–3] The high latent heat of vaporization of water is responsible for the high energy cost of drying. Multicylinder dryers[1,4,5] are the dominant configuration used in the paper industry. In multicylinder dryers, a woven dryer fabric presses the paper onto the surface of steam-heated cylinders to reduce the heat transfer contact resistance. The dryer fabric must be porous to permit the moisture transfer from the wet paper web. Typically, the paper web travels through the machine at ∼15 m/s, however modern paper machines may exceed the production speed of 30 m/s.[1] All dryer cylinders are enclosed in a well-ventilated hood to displace the humid air with dry and hot air, and boost evaporation.[1] Numerical simulations and experimental investigations have been conducted to quantify the effect of different factors (such as operating parameters, ventilation, paper type, etc.) on the efficiency of the drying.[6–11] These investigations have led to significant efficiency improvements in the drying process.[3,5,6,8,11–18]
Cleaner production solution selection for paper making – a case study of Latif paper products Co. Iran
Published in International Journal of Sustainable Engineering, 2018
Majid Azizi, Yaghoob Asadizadeh, Charles Ray, Yahya Hamzeh
The pulp and paper industry is one of the large and capital and resources (raw materials, energy, water) intensive industry that causes serious environmental problems, such as global warming, human toxicity, ecotoxicity, photochemical oxidation, acidification, nutrification and solid wastes production (Avsar and Demirer 2008; Thompson et al. 2001). Usually, the production of paper and board has four main phases, including pulp production (chemical or mechanical virgin pulp and recycled fibre pulp), stock preparation (screening, cleaning, additives application, mixing and storing and etc.) paper machine (web forming, dewatering, pressing, drying, winding), and coating and finishing. During these phases, several mechanical and thermomechanical, chemimechanical, and chemical technologies are involved resulting in various negative environmental impacts (Bajpai 2010). Considering the actual state of the art, pulp and paper mills are facing various challenges with the energy efficiency mechanism, management of the resulting pollutants and environmental issues, satisfying ongoing legal requirements and etc., (Kamali and Khodaparast 2015).
A novel thermodynamic and heat and mass transfer model for the multicylinder dryer section of a paper machine
Published in Drying Technology, 2020
Ali Anjomshoaa, Mazyar Salmanzadeh
Multicylinder dryers of paper machines consist of several steam-heated cylinders, the surface of which is in contact with wet paper web. Figure 1 shows the configuration of a two-tire, double-felted dryer system. In this type, there are two rows of cylinders with two dryer fabrics (or felts), which guide the paper web in the dryer.